In recent years, devices which handle image information in the digital form and, in this case, utilize redundancy specific to the image information to achieve compression and coding of images by using a coding scheme for compression based on an orthogonal transform such as a discrete cosine transform and motion compensation in order to efficiently transmit and accumulate information are becoming widespread. Examples of this coding scheme include MPEG (Moving Picture Experts Group) and H.264 and MPEG-4 Part 10 (Advanced Video Coding, hereinafter referred to as H.264/AVC).
In addition, standardization of a coding scheme called HEVC (High Efficiency Video Coding) is currently being undertaken by JCTVC (Joint Collaboration Team-Video Coding), which is a joint standardization organization of the ITU-T and the ISO/IEC, for achieving more improved coding efficiency than H.264/AVC (see, for example, NPL 1).
In the present working draft of HEVC, a deblocking filter, an adaptive loop filter, and an adaptive offset filter (Sample Adaptive Offset: SAO) are employed as in-loop filters.
In HEVC, parameters of the adaptive loop filter are collectively sent to the decoder side in groups of one frame. In contrast, NPL 2 has proposed that an adaptive loop filter process is performed in units of a largest coding unit, or LCU.